In a method of manufacturing a semiconductor device such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), usually a plurality of photolithography steps are performed. An alignment mark is used as a positional reference for aligning patterns with each other that are formed by the photolithography steps. Japanese Patent Laying-Open No. 2000-286179 discloses that an alignment mark may be etched in an SiO2 film on a semiconductor substrate.